A systematic review and meta-analysis of cold in situ perfusion and preservation of the hepatic allograft: Working toward a unified approach

Deceased Donor Flush Volume Similar for Histidine-Tryptophan-Ketoglutarate and University of Wisconsin at a Single US Organ Procurement Organization: Adult and Pediatric Data

BACKGROUND

Histidine-tryptophan-ketoglutarate (HTK) and University of Wisconsin (UW) solutions are the two primary solid-organ preservation solutions used in the United States (>95%), but flush volumes vary markedly by region and center. This study analyzes data from a single organ procurement organization (OPO) to determine the actual clinical flush volumes used for HTK and UW for liver and pancreas grafts.

METHODS

All procurements at Indiana Donor Network were analyzed (2016-2020), and data were extracted from the on-site records. Variables included procuring center, solution, volumes, and vessels flushed. Brand and generic versions were considered equivalent. No clinical transplant outcomes were available.

RESULTS

Data were analyzed from 875 liver and 192 pancreas procurements by over 70 U.S. centers representing 10 of 11 UNOS regions. The large majority of liver grafts were preserved with HTK (n=810, 93%; UW n=93, 7%). All liver donors received an aortic flush (100%), while portal vein flush was 14% in-situ and 88% back table. For liver grafts, the median volume of infused solution was less for HTK when compared to UW (4225mL vs 5500mL, p=0.04). For pancreas procurement, 100% received aortic flush of the graft, with median HTK and UW volumes being equivalent (3000mL; p=0.85). Pediatric organs were flushed with markedly higher weight-based volumes.

CONCLUSIONS

Flush volumes for HTK and UW are similar at one midwestern OPO, with data comprised of procurements performed by centers from across the U.S. These data demonstrate that low-volume HTK flush is commonly used, and this practice may be considered as a cost-saving measure.

Ex vivo liver resection and auto-transplantation as an alternative to treat liver malignancies: Progress and challenges

Hepatectomy is still the major curative treatment for patients with liver malignancies. However, it is still a big challenge to remove the tumors in the central posterior area, especially if their location involves the retrohepatic inferior vena cava (RHIVC) and hepatic veins. Ex vivo liver resection and auto-transplantation (ELRA), a hybrid technique of the traditional liver resection and transplantation, has brought new hope to these patients and therefore becomes a valid alternative to liver transplantation. Due to its technical difficulty, ELRA is still concentrated in a few hepatobiliary centers that have experienced surgeons in both liver resection and liver transplantation. The efficacy and safety of this technique has already been demonstrated in the treatment of benign liver diseases, especially in the advanced alveolar echinococcosis. Recently, the application of ELRA for liver malignances has gained more attention. However, standardization of clinical practice norms and international consensus are still lacking. The prognostic impact in these oncologic patients also needs further evaluation. In this review, we summarized the principles and recent progresses on ELRA.

Liver Ultrasound Histotripsy: Novel Analysis of the Histotripsy Site Cell Constituents with Implications for Histotripsy Application in Cell Transplantation and Cancer Therapy

Introduction: Allogenic hepatocyte transplantation is an attractive alternative to whole-organ transplantation, particularly for the treatment of metabolic disorders and acute liver failure. However, the shortage of human donor organs for cell isolation, the low cell yield from decellularisation regimes, and low engraftment rates from portal administration of donor cells have restricted its clinical application. Using ultrasound histotripsy to provide a nidus in the liver for direct cell transplantation offers a new approach to overcoming key limitations in current cell therapy. We have analysed the liver cavity constituents to assess their potential as a site for cell delivery and implantation. Methods: Using human organ retrieval techniques, pig livers were collected from the abattoir and transported in ice-cold storage to the laboratory. Following 2 h of cold storage, the livers were flushed with organ preservation solution and placed on an organ perfusion circuit to maintain viability. Organs were perfused with Soltran™ organ preservation solution via the portal vein at a temperature of 24-30 °C. The perfusion circuit was oxygenated through equilibration with room air. Perfused livers (n=5) were subjected to ultrasound histotripsy, producing a total of 130 lesions. Lesions were generated by applying 50 pulses at 1 Hz pulse repetition frequency and 1% duty cycle using a single element 2 MHz bowl-shaped transducer (Sonic Concepts, H-148). Following histotripsy, a focal liver lesion was produced, which had a liquid centre. The fluid from each lesion was aspirated and cultured in medium (RPMI) at 37 °C in an incubator. Cell cultures were analysed at 1 and 7 days for cell viability and a live-dead assay was performed. The histotripsy sites were excised following aspiration and H&E staining was used to characterise the liver lesions. Cell morphology was determined by histology. Results: Histotripsy created a subcapsular lesion (~5 mm below the liver capsule; size ranging from 3 to 5 mm), which contained a suspension of cells. On average, 61×10⁴ cells per mL were isolated. Hepatocytes were present in the aspirate, were viable at 24 h post isolation and remained viable in culture for up to 1 week, as determined by phalloidin/DAPI cell viability stains. Cultures up to 21 days revealed metabolically active live hepatocyte. Live-dead assays confirmed hepatocyte viability at 1 week (Day 1: 12% to Day 7: 45% live cells; p < 0.0001), which retained metabolic activity and morphology, confirmed on assay and microscopy. Cell Titre-Glo^TM showed a peak metabolic activity at 1 week (average luminescence 24.6 RLU; p < 0.0001) post-culture compared with the control (culture medium alone), reduced to 1/3 of peak level (7.85 RLU) by day 21. Conclusions: Histotripsy of the liver allows isolation and culture of hepatocytes with a high rate of viability after 1 week in culture. Reproducing these findings using human livers may lead to wide clinical applications in cell therapy.

Abdominal Organ Preservation Solutions in the Age of Machine Perfusion

The past decade has been the foreground for a radical revolution in the field of preservation in abdominal organ transplantation. Perfusion has increasingly replaced static cold storage as the preferred and even gold standard preservation method for marginal-quality organs. Perfusion is dynamic and offers several advantages in comparison with static cold storage. These include the ability to provide a continuous supply of new metabolic substrates, clear metabolic waste products, and perform some degree of organ viability assessment before actual transplantation in the recipient. At the same time, the ongoing importance of static cold storage cannot be overlooked, in particular when it comes to logistical and technical convenience and cost, not to mention the fact that it continues to work well for the majority of transplant allografts. The present review article provides an overview of the fundamental concepts of organ preservation, providing a brief history of static cold preservation and description of the principles behind and basic components of cold preservation solutions. An evaluation of current evidence supporting the use of different preservation solutions in abdominal organ transplantation is provided. As well, the range of solutions used for machine perfusion of abdominal organs is described, as are variations in their compositions related to changing metabolic needs paralleling the raising of the temperature of the perfusate from hypothermic to normothermic range. Finally, appraisal of new preservation solutions that are on the horizon is provided.

Experimental long-term sub-normothermic machine perfusion for non-allocable human liver grafts: first data towards feasibility

Background

Patients with end-stage liver disease can only be cured by liver transplantation. Due to the gap between demand and supply, surgeons are forced to use expanded criteria donor (ECD) organs, which are more susceptible to ischemia–reperfusion injury (IRI). Therefore, enhanced storing techniques are required. Machine perfusion (MP) has moved into the spotlight of research because of its feasibility for investigating liver function prior to implantation. However, as the perfect MP protocol has not yet been found, we aimed to investigate the potential of sub-normothermic (SN)MP in this field.

Methods

Non-allocable human livers were subjected to 24 h of SNMP at 21 °C after delivery to the study team. Perfusion was performed with Custodiol® (Dr. Franz Köhler Chemie, Bensheim, Germany) or Belzer MPS® (Bridge to Life Europe, London, UK) and perfusate liver parameters were determined. For determination of biliary conditions, pH, glucose, and HCO3- levels were measured.

Results

Liver parameters were slightly increased irrespective of perfusate or reason for liver rejection during 24 h of perfusion. Six livers failed to produce bile completely, whereas the remaining 10 livers produced between 2.4 ml and 179 ml of bile. Biliary carbonate was increased in all but one liver. The bile-glucose-to-perfusate-glucose ratio was near 1 for most of the organs and bile pH was above 7 in all but one case.

Conclusion

This study provides promising data on the feasibility of long-term SNMP as a tool to gain time during MP to optimize ECD organs to decrease the gap between organ demand and supply.

Long-term (24 h) sub-normothermic liver machine perfusion seems to be possible, although some adjustments to the protocol might be necessary to improve the general outcome. This has so far been shown for normothermic machine perfusion, bearing some drawbacks compared to the sub-normothermic variant.

Graft weight integration in the early allograft dysfunction formula improves the prediction of early graft loss after liver transplantation

The role of the graft-to-recipient weight ratio (GRWR) in adult liver transplantation (LT) has been poorly investigated so far. The aim is to evaluate the contribution of the GRWR to the well-recognized early allograft dysfunction (EAD) model (i.e., Olthoff model) for the prediction of 90-day graft loss after LT in adults. Three hundred thirty-one consecutive adult patients undergoing LT between 2009 and 2018 at Tor Vergata and Sapienza University in Rome, Italy, served as the Training-Set. The Validation-Set included 123 LTs performed at the Erasmus Medical Center, Rotterdam, the Netherlands. The mEAD model for 90-day graft loss included the following variables: GRWR \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le $$\end{document}≤ 1.57 = 2.5, GRWR \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\ge $$\end{document}≥ 2.13 = 2.5, total bilirubin ≥ 10.0 mg/dL = 2.0, INR ≥ 1.60 = 2.3, and aminotransferase > 2000 IU/L = 2.2. The mEAD model showed an AUC = 0.74 (95%CI = 0.66–0.82; p < 0.001) and AUC = 0.68 (95%CI = 0.58–0.88; p = 0.01) in the Training-Set and Validation-Set, respectively, outperforming conventional EAD in both cohorts (Training-Set: AUC = 0.64, 95%CI = 0.57–0.72; p = 0.001; Validation-Set: AUC = 0.52, 95%CI = 0.35–0.69, p = 0.87). Incorporation of graft weight in a composite multivariate model allowed for better prediction of patients who presented an aminotransferase peak > 2000 IU/L after LT (OR = 2.39, 95%CI = 1.47–3.93, p = 0.0005). The GRWR is important in determining early graft loss after adult LT, and the mEAD model is a useful predictive tool in this perspective, which may assist in improving the graft allocation process.

The effect of organ preservation solutions on short-term outcomes after liver transplantation: a single-center retrospective study

The effect of preservation solutions on outcomes has been subject of many debates but the relative benefits of the various solutions remain unclear. We retrospectively compared short-term outcomes of 885 liver transplantations performed between 1/2000 and 12/2017 and preserved with either Histidine-Tryptophan-Ketoglutarate (HTK, n = 190), University of Wisconsin (UW, n = 557), or Institute George Lopez 1 preservation solution (IGL-1, n = 139). Inverse probability of treatment weighting (IPTW) was performed to account for baseline differences between groups and analyses were adjusted for confounders. In the IPTW analyses, peak AST within 7 days was 44% higher (95% CI 15-81%, P < 0.001) in HTK than in UW. Mean model of early allograft function (MEAF) score was 0.61 points (95% CI 0.12-1.10, P = 0.01) higher in HTK than in UW. Early allograft dysfunction (EAD) was more likely to occur with HTK compared to IGL-1 (IPTW OR = 2.87, 95% CI = 1.00-8.19, P = 0.049) and UW (IPTW OR = 1.75, 95% CI = 1.06-2.88, P = 0.023). The type of preservation solution had no impact on hospital stay, ICU stay, incidence of biliary strictures, or graft and recipient survival. HTK was the least effective on reducing graft injury and increased the probability of graft dysfunction after transplantation. UW and IGL-1 were equally effective in reducing graft injury and dysfunction.

Morphologic assessment of hypertonic citrate adenine, histidine-tryptophan-ketoglutarate, and university of Wisconsin solutions for hypothermic uterus preservation in rats

AIM

Optimizing perfusate for static cold storage is one of the key ways of reducing organ dysfunction and rejection in organ transplantation. Here, we tested the effectiveness of the three different solutions for hypothermic uterus preservation.

METHODS

Twenty rats were divided into four groups, five in each group. Uterine grafts were retrieved and perfused in situ. The uteri were preserved at 4°C in normal saline as control group (group NS), hypertonic citrate adenine (group HCA), histidine-tryptophan-ketoglutarate (group HTK), or university of Wisconsin solutions (group UW) for 0, 12, 24, and 48 h, respectively. HE, electron microscopy, TUNEL staining, and Cleaved Caspase3 immunohistochemical staining were assessed at each time point.

RESULTS

There was no significant difference in the uterine retrieval time, perfusion time, and the amount of perfusion solution in NS, HCA, HTK, and UW groups (p > 0.05). HCA and HTK can well preserve the pathological morphology of rat uterine tissues for up to 24 h, and the apoptosis rates of the two groups are 7.2% and 7.1%, respectively, with no statistical difference (p > 0.05). Still, the protective effect of HTK on the ultrastructure of cells was much better than HCA. There was a significant difference in the apoptosis rate of UW (6.5%), HTK (8.8%), and HCA (9.4%) at 48 h, with mitochondrial and endoplasmic reticulum structure well preserved only in UW.

CONCLUSION

At 4°C, normal saline is not suitable to preserve rat uterus for more than 12 h. The morphologic results would favor the use of HTK rather than HCA for short-term hypothermic uterus preservation (≤24 h). UW is better than HTK and HCA for 48 h hypothermic uterus preservation.

A Systematic Review and Meta-Analysis of Machine Perfusion vs. Static Cold Storage of Liver Allografts on Liver Transplantation Outcomes: The Future Direction of Graft Preservation

Background: Machine perfusion (MP) and static cold storage (CS) are two prevalent methods for liver allograft preservation. However, the preferred method remains controversial.

Aim: To conduct a meta-analysis on the impact of MP preservation on liver transplant outcome.

Methods: PubMed, EMBASE, and Cochrane Library databases were systematically searched to identify relevant trials comparing the efficacy of MP vs. CS. Odds ratios (OR) and fixed-effects models were calculated to compare the pooled data.

Results: Ten prospective cohort studies and two randomized controlled trials (RCTs) were included (MP livers vs. CS livers = 315:489). Machine perfusion demonstrated superior outcomes in posttransplantation aspartate aminotransferase levels compared to CS (P < 0.05). The overall incidence of early allograft dysfunction (EAD) was significantly reduced with MP preservation than CS [OR = 0.46; 95% confidence interval (CI) = 0.31–0.67; P < 0.0001]. The incidence of total biliary complications (OR = 0.53; 95% CI = 0.34–0.83; P = 0.006) and that of ischemic cholangiopathy (OR = 0.39; 95% CI = 0.18–0.85; P = 0.02) were significantly lower in recipients with MP preservation compared with CS preservation. Hypothermic machine perfusion (HMP) but not normothermic machine perfusion (NMP) was found to significantly protect grafts from total biliary complications and ischemic cholangiopathy (P < 0.05). However, no significant differences could be detected utilizing either HMP or NMP in primary nonfunction, hepatic artery thrombosis, postreperfusion syndrome, 1-year patient survival, or 1-year graft survival (P > 0.05).

Conclusions: Machine perfusion is superior to CS on improving short-term outcomes for human liver transplantation, with a less clear effect in the longer term. Hypothermic machine perfusion but not NMP conducted significantly protective effects on EAD and biliary complications. Further RCTs are warranted to confirm MP's superiority and applications.

Systematic Review: Clinical Metabolomics to Forecast Outcomes in Liver Transplantation Surgery

Liver transplantation is an effective intervention for end-stage liver disease, fulminant hepatic failure, and early hepatocellular carcinoma. Yet, there is marked patient-to-patient variation in liver transplantation outcomes. This calls for novel diagnostics to enable rational deployment of donor livers. Metabolomics is a postgenomic high-throughput systems biology approach to diagnostic innovation in clinical medicine. We report here an original systematic review of the metabolomic studies that have identified putative biomarkers in the context of liver transplantation. Eighteen studies met the inclusion criteria that involved sampling of blood (n = 4), dialysate fluid (n = 4), bile (n = 5), and liver tissue (n = 5). Metabolites of amino acid and nitrogen metabolism, anaerobic glycolysis, lipid breakdown products, and bile acid metabolism were significantly different in transplanted livers with and without graft dysfunction. However, criteria for defining the graft dysfunction varied across studies. This systematic review demonstrates that metabolomics can be deployed in identification of metabolic indicators of graft dysfunction with a view to implicated molecular mechanisms. We conclude the article with a horizon scanning of metabolomics technology in liver transplantation and its future prospects and challenges in research and clinical practice.

Heterogeneity of Bile Duct Management in the Development of Ischemic Cholangiopathy After Liver Transplantation: Results of a European Liver and Intestine Transplant Association Survey

BACKGROUND

Surgical factors and direct cytotoxicity of bile salts on cholangiocytes may play a role in the development of ischemic cholangiopathy (IC) after liver transplantation (LTx). There is no validated consensus on how to protect the bile ducts during procurement, static preservation, and LTx. Meanwhile, IC remains the most troublesome complication after LTx.

AIM

To characterize bile duct management techniques during the LTx process among European transplant centers in cases of donation after brain death (DBD) and circulatory death (DCD).

METHOD

An European Liver and Intestine Transplant Association-European Liver Transplant Registry web survey designed to conceal respondents' personal information was sent to surgeons procuring and/or transplanting livers in Europe.

RESULTS

Sixty-five percent of responses came from large transplant centers (>50 procurements/y). In 8% of DBDs and 14% of DCDs the bile duct is not rinsed. In 46% of DBDs and 52% of DCDs surgeons prefer to remove the gallbladder after graft reperfusion. Protocols concerning preservation solutions (nature, pressure, volume) are extremely heterogeneous. In 54% of DBDs and 61% of DCDs an arterial back table pressure perfusion is performed. Steroids (20%-10%), heparin (72%-60%), prostacyclin (3%-7%), and fibrinolytics (4%-11%) are used as donor-protective interventions in DBD and DCD cases, respectively. In 2% of DBD and 6% of DCD cases a hepatic artery reperfusion is performed first. In 4% of DBD and 6% of DCD cases, fibrinolytics are administered through the hepatic artery during the bench and/or implantation.

CONCLUSION

This European web survey shows for the first time the heterogeneity in the management of bile ducts during procurement, preservation, and transplantation in Europe. In the context of sharing more marginal liver grafts, an expert meeting must be organized to formulate guidelines to be applied to protect liver grafts against IC.

Abdominal wall transplantation in organ transplantation: Our experience

Abdominal wall transplantation has been consolidated as an alternative to primary abdominal wall closure in intestinal and multiple organ transplant recipients. Given that it is feasible to obtain the visceral graft and the abdominal wall graft from the same donor, abdominal wall transplantation could offer satisfactory outcomes and be easily coordinated. Non-vascularized fascia is one of the alternatives for abdominal wall closure in transplantation. We report two cases of non-vascularized fascia transplantation in intestinal and multivisceral transplants, respectively. Both donors were young (23 and 18 years old). Both recipients had endured multiple previous surgeries, and no surgical alternatives for primary wall repair could be offered. In both cases, a complete abdominal wall flap was retrieved from the donor, however, due to the characteristics of the recipient's abdominal wall defect, only non-vascularized fascia was used after removing skin and subcutaneous cellular tissue from the graft. Abdominal wall transplantation is an option to consider for abdominal wall closure in patients with multiple previous surgeries and no alternatives for primary wall repair.

Policies towards donation after circulatory death liver transplantation: the need for a guideline?

BACKGROUND

Liver transplantation (LT) using grafts from donation after circulatory death (DCD) is evolving to standard of care in many countries. Various transplant centers have developed a protocol for DCD-LT. The existence of numerous protocols may cause inconsistencies. Knowledge of these differences may help improve the outcome of DCD-LT.

METHODS

An internet-based survey was sent to 119 transplant surgeons among four countries: Belgium (BE), the Netherlands (NL), Spain (ES) and the United Kingdom (UK).

RESULTS

Thirty-three percent of all respondents indicated having no specific age limit for DCD-LT donors, and if there was a limit, half of them ignored it. Calculation of donor warm ischemia time (dWIT) varied substantially between countries. In ES and the UK, the starting point of dWIT was defined as deterioration of saturation/blood pressure, while in NL, cardiac arrest was used as starting point. Seventy-eight percent of the respondents used a super-rapid sterno-laparotomy as procurement technique. Surgeons from NL and BE mainly used aortic perfusion (95% and 72%), while dual perfusion was more common in the UK (90%) and ES (91%).

CONCLUSIONS

This study demonstrates major differences in approach to DCD-LT. To assure both donors and recipients a consistent standard of care, a consensus meeting on DCD-LT is highly recommended.

Aortic Versus Dual Perfusion for Retrieval of the Liver After Brain Death: A National Registry Analysis

There is lack of consensus in the literature regarding the comparative efficacy of in situ aortic-only compared with dual (aortic and portal venous) perfusion for retrieval and transplantation of the liver. Recipient outcomes from the Australia/New Zealand Liver Transplant Registry (2007-2016), including patient and graft survival and causes of graft loss, were stratified by perfusion route. Subgroup analyses were conducted for higher-risk donors. A total of 1382 liver transplantation recipients were analyzed (957 aortic-only; 425 dual perfusion). There were no significant differences in 5-year graft and patient survivals between the aortic-only and dual cohorts (80.1% versus 84.6% and 82.6% versus 87.8%, respectively) or in the odds ratios of primary nonfunction, thrombotic graft loss, or graft loss secondary to biliary complications or acute rejection. When analyzing only higher-risk donors (n = 369), multivariate graft survival was significantly less in the aortic-only cohort (hazard ratio, 0.49; 95% confidence interval, 0.26-0.92). Overall, there was a trend toward improved outcomes when dual perfusion was used, which became significant when considering higher-risk donors alone. Inferences into the ideal perfusion technique in multiorgan procurement will require further investigation by way of a randomized controlled trial, and outcomes after the transplantation of other organs will also need to be considered.

Dual aortic and portal perfusion at procurement prevents ischaemic-type biliary lesions in liver transplantation when using octogenarian donors: a retrospective cohort study

Several risk factors for ischaemic-type biliary lesions (ITBL) after liver transplantation (LT) have been identified, but the role of portal vein perfusion at graft procurement is still unclear. This was a prospective study on double aortic and portal perfusion (DP) of liver grafts stratified by donor's decade (<60 yo; 60-69 yo; 70-79 yo and ≥80 yo) versus similar historical cohorts of primary, adult grafts procured with single aortic perfusion (SP) only. The primary study aim was to assess the role of DP on the incidence of ITBL. There was no difference in the incidence of overall biliary complications according to procurement technique for recipients of grafts <80 years. A higher incidence of ITBL was observed for patients receiving grafts ≥80 years and perfused through the aorta only (1.9 vs. 13.4%; P = 0.008). When analysing octogenarian grafts, donor male gender (HR = 6.4; P = 0.001), haemodynamic instability (HR = 4.9; P = 0.008), and type-2 diabetes mellitus (DM2) (HR = 3.0; P = 0.03) were all independent risk factors for ITBL, while double perfusion at procurement (HR = 0.1; P = 0.04) and longer donor intensive care unit (ICU) stay (HR = 0.7; P = 0.04) were protective factors. Dual aortic and portal perfusion has the potential to reduce post-transplant ITBL incidence for recipients of octogenarian donor grafts. Larger series are needed to confirm this preliminary experience.

Angiotensin IV improves subnormothermic machine perfusion preservation of rat liver graft

This study aims to determine whether Angiotensin IV (Ang IV) addition to Celsior preservation solution could improve hepatic endothelium function and provide better liver protection during subnormothermic machine preservation (SMP). Two experimental models were used: In the first part of the study, rings isolated from rat hepatic artery were preserved in Celsior solution (6 h, 20 °C) with and without Ang IV (10^-9 M), then, endothelium-dependent relaxation (EDR) and the concentration of acetylcholine inducing half-maximal relaxation of pre-contracted rings (EC50) were measured. Also, in order to investigate the implication of nitric oxide (NO) on EDR, the rings of hepatic artery were incubated with L-NG-nitroarginine metyl ester (L-NAME). In the second part of the study, rat livers were subjected to SMP with oxygenated Celsior solution (6 h, 20 °C), supplemented or not with Ang IV (10^-9 M) and then perfused (2 h, 37 °C) with Krebs Henseleit solution. We found that Ang IV supplementation to Celsior solution decreased EC50 value and improved EDR of hepatic artery rings, 6h after sub-normothermic preservation. Interestingly, Ang IV amplified the vessel relaxation in a NO-dependent manner. Moreover, liver SMP with Ang IV reduced oxidative stress and cell injury and improved organ function. Ang IV activated pAkt, increased eNOS protein level and decreased apoptosis in the preserved liver grafts. In conclusion, we showed that the use of Ang IV in Celsior solution for sub-normothermic graft preservation insured a better NO-dependent relaxation and improved liver functional recovery.